curl --request POST \
  --url https://api.example.com/api/v1/staking/transactions/build \
  --header 'Content-Type: application/json' \
  --data '
{
  "productId": "base_usdc_nexfi_vault",
  "orderType": "subscribe",
  "walletAddress": "0xabc1230000000000000000000000000000000000",
  "amount": "1000"
}
'

{
  "code": 0,
  "msg": "ok",
  "data": {
    "buildId": "build_20260511_0001",
    "chainId": 8453,
    "to": "0xvault000000000000000000000000000000000001",
    "value": "0",
    "data": "0xb6b55f25",
    "gasLimit": "280000",
    "warnings": [
      "APY is estimated and not guaranteed"
    ],
    "sharesPreview": "998.12",
    "feePreview": "1.50",
    "vaultAddress": "0xvault000000000000000000000000000000000001"
  }
}